Centrifugal fan

ABSTRACT

A centrifugal fan includes a spiral housing, a driving mechanism and multiple internally mounted impellers. The driving mechanism and the centrifugal impeller, rotated by the driving mechanism, are installed in the spiral housing. A spiral flow channel is defined between the centrifugal impeller and the spiral housing. When the centrifugal impeller rotates, airflow is sucked axially into the spiral housing through an inlet opening and moves along each blade of the centrifugal impeller into the spiral flow channel. The centrifugal impeller includes a hub and multiple blades. Each blade is secured to the hub at one end and has at least one vertical convex strip or vertical concave strip at an opposite end, wherein the vertical convex strip or vertical concave strip on each of blade disturbs the airflow across thereof and reduces narrow-band noise.

RELATED APPLICATIONS

The present application is based on, and claims priority from, Taiwan Application Serial Number 95114589, filed on Apr. 24, 2006, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

1. Field of Invention

The present invention relates to a centrifugal fan. More particularly, the present invention relates to a centrifugal fan with noise reduction functionality.

2. Description of Related Art

As notebook PCs become thinner, less space is available for heat convection and heat dissipation components inside the notebook PC case housing. High-frequency components, such as the CPU (central processing unit) and graphics processing chip, also place limitations on heat dissipation designs. Thus, the mainstream method to dissipate heat is forced heat convection via a centrifugal fan.

A centrifugal fan employs a spiral flow channel design to convert dynamic air energy into static pressure so as to overcome the high air flow impedance inside the notebook PC case housing. However, high static pressure generating centrifugal fans face the dual challenge of reducing noise and improving heat dissipation efficiency. Noise can be divided into broadband noise and narrowband noise, wherein narrowband noise is preferably eliminated from a centrifugal fan.

FIG. 1 illustrates a perspective view of a conventional centrifugal fan. A centrifugal fan 100 includes a spiral housing 102, which has a motor (not illustrated) and an internal centrifugal impeller 104. When the motor rotates the centrifugal impeller 104, driven airflow moves along a spiral flow channel 110. A wake flow 112, coming out of blades 106 of the centrifugal impeller 104, crashes against the inner walls of the spiral flow channel 110, thereby creating a BPF (Blade Pass Frequency). BPF often becomes high-frequency, narrow-band noise, especially in a high static pressure generating centrifugal fan. BPF also generates an annoying high-frequency, narrow-band noise when the wake flow 112 hits a cut-off 103 of a centrifugal fan 100.

SUMMARY

It is therefore an objective of the present invention to provide a centrifugal fan with a noise reduction functionality so as to reduce noise and improve the overall heat dissipation efficiency.

In accordance with the foregoing and other objectives of the present invention, a centrifugal fan includes a spiral housing, a driving mechanism and multiple internally mounted impellers. The driving mechanism and the centrifugal impeller, rotated by the driving mechanism, are installed in the spiral housing. A spiral flow channel exists between the centrifugal impeller and the spiral housing. When the centrifugal impeller rotates, airflow is sucked axially into the spiral housing through an inlet opening and moves along each blade of the centrifugal impeller into the spiral flow channel. The centrifugal impeller includes a hub and multiple blades. Each of the blades is secured to the hub at one end and has at least one vertical convex strip or vertical concave strip at an opposite end, wherein the vertical convex strip or vertical concave strip on each blade disturbs the airflow across thereof and reduces narrow-band noises.

Thus, each blade of the centrifugal fan has a vertical convex strip or a vertical concave strip at an end of the windward side so as to disturb airflows across thereof, thereby decreasing high-frequency and narrow-band noises. Such centrifugal impeller design overcomes a challenge between noise reducing and heat dissipation efficiency improving in a notebook computer.

It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings,

FIG. 1 illustrates a perspective view of a conventional centrifugal fan;

FIG. 2 illustrates a cross-sectional view of a centrifugal fan according to one preferred embodiment of this invention; and

FIGS. 3A and 3B respectively illustrate two types of centrifugal impellers according to one preferred embodiment of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

FIG. 2 illustrates a cross-sectional view of a centrifugal fan according to one preferred embodiment of this invention. A centrifugal fan 200 has a spiral housing 202. A centrifugal impeller and a driving mechanism 208 (such as a motor) are installed in the spiral housing 202. The centrifugal impeller includes a hub 204 and multiple blades 206 (like blades 106 in FIG. 1). When the driving mechanism 208 rotates the centrifugal impeller, rotating blades 206 constantly suck airflow along the direction 214. The airflow moves axially into the spiral housing 202 through an inlet opening 202 a, and then moves along each of blades 206 (i.e. along the direction 216), and finally into a spiral flow channel 207 (like the spiral flow channel 110 in FIG. 1). In order to distribute the airflow in the direction 216, a vertical convex strip 205 a or a vertical concave strip 205 b is formed at the end and the windward side of each blade 206 to disturb the airflow across thereof. On the contrary, a conventional blade has a flat surface on its windward side such that the airflow along the direction 216 has a bigger impact against the spiral flow channel 207 (i.e. inner walls of the housing 202). The bigger the impact against the spiral flow channel 207, the more high-frequency and narrow-band noises are generated.

In this preferred embodiment, a width d of the vertical convex strip 205 a or the vertical concave strip 205 b is approximately equal to the thickness of the blade 206. However, the width d is not a constant value and its optimum value could vary according to the blade length, blade rotation speed, flow channel shape etc, and does not influence the dissipation performance of the centrifugal fan. More than one vertical convex strip 205 a or vertical concave strip 205 b may be formed on the blade 206 as long as the dissipation performance of the centrifugal fan is not influenced.

FIGS. 3A and 3B respectively illustrates two types of centrifugal impellers according to one preferred embodiment of this invention.

In FIG. 3A, a hub 204 and one blade 206 a of blades 206 are illustrated. The hub 204 and the blade 206 a both rotate in the direction 210. The vertical concave strips 205 a are formed on the windward side of the blade 206 a, and the airflow 212 a is therefore disturbed and its impact on the cut-off 203 (like the cut-off 103 in FIG. 1) is reduced, thereby decreasing the high-frequency, narrow-band noise.

In FIG. 3B, a hub 204 and one blade 206 b of the blades 206 are illustrated. The hub 204 and the blade 206 b both rotate in the direction 210. The vertical convex strips 205 b are formed on the windward side of the blade 206 b, and the airflow 212 b is therefore disturbed and its impact on the cut-off 203 (like cut-off 103 in FIG. 1) is reduced, thereby decreasing the high-frequency and narrow-band noises.

According to the preferred embodiments of the present invention, each blade of the centrifugal fan has a vertical convex strip or a vertical concave strip at the end of the blade, at the windward side so as to disturb the airflow across thereof, thereby decreasing the high-frequency, narrow-band noise. Such a centrifugal impeller design reduces noise and improves heat dissipation efficiency in a notebook PC.

It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents. 

1. A centrifugal fan, comprising: a housing, having an inlet opening; a driving mechanism mounted in the housing; a centrifugal impeller, driven by the driving mechanism, a flow channel is defined between the centrifugal impeller and the housing, the centrifugal impeller comprising: a hub; and multiple blades, each of the multiple blades secured to the hub at one end and having at least one vertical convex strip at an opposite end, when the centrifugal impeller rotates, airflow is sucked axially into the housing through the inlet opening, and moves along each of the multiple blades, wherein the vertical convex strip at each of the multiple blades disturbs the airflow across thereof and reduces narrow-band noises.
 2. The centrifugal fan of claim 1, wherein the driving mechanism is a motor.
 3. A centrifugal fan, comprising: a housing, having an inlet opening; a driving mechanism, mounted in the housing; a centrifugal impeller, driven by the driving mechanism, a flow channel is defined between the centrifugal impeller and the housing, the centrifugal impeller comprising: a hub; and multiple blades, each of the multiple blades secured to the hub at one end and having at least one vertical concave strip at an opposite end, when the centrifugal impeller rotates, airflow is sucked axially into the housing through the inlet opening, and moves along each of the multiple blades, wherein the vertical concave strip at each of the multiple blades disturbs the airflow across thereof and reduces narrow-band noise.
 4. The centrifugal fan of claim 3, wherein the driving mechanism is a motor. 